New Game: how'd I roach that piston?

[1100s nut]

How did your plugs look last change out? I`m just wondering, white with a lot of spatter or brown normal looking? Sorry to see your problem. It can happen to any brand though.

Lane

[Guest24]

I'm going to say that the oiler and compression rings all got in perfect alignment and the blow by melted the piston on its journey to the bottom end as long as we're making wild a$$ guesses.

[dee jones]

I'd say its a mystery until its solved.

Sorry for the pain in the ass, not to mention your pocket book. Swarty seems to be close on this one. Good luck with the 1150 upgrade.

[signit98]

Originally Posted by bigscience

this is worse than owning a boat.

NO, IT'S NOT... at least not when your boat sits in salt water, trust me!

[bill pierce]

Originally Posted by Yeskino

Looks like possible detonation.

Thats kinda what it looks like to me too. However detonation is most often seen in the center of the piston. It looks like the top of the piston had been errodeing away for some time before ring failure occurred.

Have you alerted the timing? Running nitro methane perhaps??

[bigscience]

markjenn, I backed up with a honda. but the forks are out getting re-valved so I got three bikes and none on the road.

I'm definitely sending the injectors out for testing, then cleaning. I really have to hit a firm conclusion on this so I can be sure it doesn't happen again.

[bigscience]

I don't think this is a big problem with BMW's. after all part of the mystery is that no one has ever seen this before.

the plugs look great. NGK Iridium.

Nail, that was the first thing we checked. the rings were perfectly placed and other than the obvious showed no wear or other signs of degradation. I think the rings put up a pretty good fight, considering. they were burned clear through or even blasted through the hole on failure.

the injectors seem the best wild ass guess so far. that hypothesis should be easy enough to test though. there were no changes to the timing and the bike ran fine- no detonation that I could feel or hear and the bike always got high test fuel -- but not nitro methane!

ok, maybe not worse than a boat. but still money that could be used elsewhere. Found myself cruzing the want ads for Stearman Biplanes last night; now that's worse than a boat.

[Bob Hancock]

Originally Posted by bigscience

Found myself cruzing the want ads for Stearman Biplanes last night; now that's worse than a boat.

If you are serious about this, might also consider a Waco UPF-7. Has the panache of a Stearman but with 4 ailerons.

[R111S]

I run Chevron Techron Fuel System Cleaner through all my motors twice a year...keeps the injector spray pattern in good shape I hope.

[wswartzwel]

Originally Posted by bigscience

the injectors seem the best wild ass guess so far. that hypothesis should be easy enough to test though. there were no changes to the timing and the bike ran fine- no detonation that I could feel or hear and the bike always got high test fuel -- but not nitro methane!
.

I see pistons that look just like yours quite frequently on Wave Runners and JetSkiis, after people let them set over the winter with fuel in the carbs...The carbs clog up with varnish.. then they go out next summer and run them across the lake lean...starving for fuel

Presto... melted piston.

Also...Be sure to check the wiring that runs that injector.... Injector could be good, but resistance from a bad, or dirty connection could cause the injector to not supply enough fuel.













.

[markjenn]

Originally Posted by wswartzwel

I see pistons that look just like yours quite frequently on Wave Runners and JetSkiis, after people let them set over the winter with fuel in the carbs...The carbs clog up with varnish.. then they go out next summer and run them across the lake lean...starving for fuel

Presto... melted piston.

But these are two-strokes, right? Completely different animal.

- Mark

[wswartzwel]

In what way Mark? The only difference would be the addition of a little oil in the cylinder.

I can accept people not believing me.. Living in Arkansas doesn't do much for my credibilty, nor does my online clowning/joking persona. You can do a google search for images for pistons... Detonation breaks/fractures the piston and ring lands (the area between the rings) while a lean condition melts pistons, and also causes the piston to expand and then metal transfers from the piston to the cylinder.




Again... The injector may not be getting enough electricty... If the injector checks out good.. be sure to inspect the wiring.

[wswartzwel]

BigScience... You stated that you got Chris Hodson's opinion on the failure... but you never told us what it was??? What did he think caused the failure?

[roger albert]

I'm with Bill,

This looks classic lean. In this case, it looks the same, 2 or 4 strokes.
I can't be sure though. It's hard to tell once things get too chewed up.
I too would be interested in what Chris had to say.

Sorry you're having to deal with it though bigscience. What a bite in the ass.

[markjenn]

My point is mainly that it is pretty easy to roach a two-stroke with lean jetting, but four-strokes are much more tolerant of abuse in this regard. This engine didn't fail the first time it was fired up after winter and run across a lake, it failed 40K miles after a rebuild. Whatever caused the problem is likely to be progressive and subtle, whereas you can seize most two-strokes in a matter of seconds if you get the mixture way off.

I'm not betting on mixture as the problem.

- Mark

[throttlemeister]

Mark, the rebuild failure history could be completely unrelated and irrelevant and just throwing sand in our eyes. A lean condition could be caused by an injector getting clogged up over the winter, or an injector not getting sufficient power to fire properly, or possibly a fuel pump not providing enough pressure, or a combination due to low system voltage from a broken rectifier.

[PFFOG]

Originally Posted by roger albert

I'm with Bill,

This looks classic lean. In this case, it looks the same, 2 or 4 strokes.
I can't be sure though. It's hard to tell once things get too chewed up.
I too would be interested in what Chris had to say.

Sorry you're having to deal with it though bigscience. What a bite in the ass.

Wait, lean roaches pistons, that cant be true.

You see my Great Uncles-Cousins-brothers-nephew (that is your sister in Arkansas) had this new Ford F150 he bought in the 70's and it got 70 miles to the gallon, he was ecstatic. After a month he got a frantic call from the Ford factory that there was an urgent recall on his new truck so he took it in and they changed the carb, after that he could only get 15 MPG. After researching it, he found that Big oil companies had paid off auto makers to not use the special carbs and cut into their profits.

See so it can't be true that lean is bad

[gigantic]

Originally Posted by wswartzwel

I see pistons that look just like yours quite frequently on Wave Runners and JetSkiis, after people let them set over the winter with fuel in the carbs...The carbs clog up with varnish.. then they go out next summer and run them across the lake lean...starving for fuel

Presto... melted piston.

Also...Be sure to check the wiring that runs that injector.... Injector could be good, but resistance from a bad, or dirty connection could cause the injector to not supply enough fuel.

.

[PFFOG]

http://www.laskeyracing.com/shop/breakin.htm


The 2nd half of this page offers further explanation of what lean does.

[roger albert]

Yup, It's absolutely CLASSIC looking lean. Sure, it _could_ be something else, as there are a LOT of ways for a motor to fail, but if you actually work on them, you begin seeing patterns. Ones that aren't too hard to I.D.